There were several types of rotary engine under development around the world, from among which Mazda adopted the Wankel variety. To acquire knowhow, Mazda sent a team of engineers to a West German company called NSU. There, the team found that there was a huge technological obstacle to the development in the form of “chatter marks.”The Wankel rotary engine is characterized by the unique triangular shape of its rotor. As the rotor turns at high speed, the apex seal, which is attached to each apex of the triangle to ensure air tightness, undergoes friction with the inside surface of the cocoon-shaped rotor housing